The housing of rotary vane pumps or machines usually consists of an annular casing having two covers for the circular end openings of the casing. The cover facing away from the drive motor of the pump generally has a flange projecting over the circumference of the annular casing or, in the alternative, several projecting catches which are used for fixing the pump to its drive motor housing with the aid of long screws. However, with such conventional arrangements, there is a risk of the housing being somewhat squeezed or compressed when such fixing screws are tightened. The resulting reduction in the axial clearance between the rotor and housing may cause the rotor and vanes to bind or jam in the pump or the machine housing and bearings may be improperly tilted on the drive motor housing if the screws are tightened unevenly, which may lead to not only leakage between the annular casing and its covers but also to cracks or splits in the housing itself.
Furthermore, with such prior art designs it was necessary to provide special connecting pipes leading from the pump housing for the suction and delivery connections for the outgoing air and lubricant.